The field of the disclosure relates generally to turbofan engines and, more particularly, to a method and system for suppressing resonance in fuel manifolds of turbofan engines.
Under certain operating conditions, turbofan engines experience high-frequency fuel flow oscillations into the combustor associated with fuel-coupled combustor dynamics that may negatively impact engine performance. Typically, fuel-coupled combustor dynamics may occur when combustor discharge pressure, vibration of the fuel manifold, in particular in the tangential direction, and the fuel pressure pulsation within the fuel manifold may resonate with one another and form an instability loop. For instance, when the combustor operates at low combustor discharge temperature with high main flow split, combustor discharge pressure may have high amplitude at acoustic frequency range, which drives vibration of the engine including the fuel manifolds. The vibration of the fuel manifolds in the tangential direction in turn drives high amplitude manifold pressure oscillations which in turn drive high amplitude fuel flow oscillations into the combustor.
One existing strategy to mitigate the effects of fuel-coupled combustor dynamics is to limit the amount of main fuel flow into the combustor to avoid operation within the acoustic zone. However this approach may impact emissions and Specific Fuel Consumption (SFC), thereby degrading the operational efficiency of the engine. In addition, the identification of operational parameters suitable for avoiding undesired acoustics is typically mapped empirically through engine testing. Although margins of error are typically incorporated into the resulting maps, the engine is still vulnerable to engine to engine variations, operating environment, fuel property variations, etc.
Other existing strategies incorporate devices that actively tune fuel manifold pressure frequency or directly modify combustion processes to mitigate the effects of fuel-coupled combustor dynamics. However, such devices add weight and cost to the engine and associated aircraft, and may additionally impact engine performance.